Construction hoist system

ABSTRACT

A versatile construction hoist system comprises a hoist trolley having a first pair of connection members, and a work platform having a second pair of connection members. The work platform is releasably connectable to the trolley through interconnection of the first and second pairs of connection members with the work platform in a horizontal position in which the work platform floor is situated at the first level relative the trolley. A transport platform, which has a third pair of connection members, is releasably connectable to the trolley through interconnection of the first and third pairs of connection members with the transport platform in a horizontal position in which its floor is situated at a second level relative the trolley, said second level being below said first level. An adapter enables use of standard transport platform elements.

CROSS REFERENCE TO RELATED APPLICATION

This application is a U.S. national phase of PCT/SE99/00492 filed Mar.26, 1999.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a construction hoist system, comprisingat least one mast having two adjacent parallel corner rails, a trolleyrunning on the corner rails, and a motor on the trolley for driving thetrolley along the corner rails. The system further comprises a firstpair of connection members on the trolley, a work platform having asubstantially flat work floor, and a second pair of connection memberson the work platform. The work platform is releasably connectable to thetrolley through interconnection of the first and second pairs ofconnection members with the work platform in a horizontal position inwhich the work floor is situated at a first level relative the trolley.

Such a construction hoist system is disclosed in SE-B-462 336. At oneend the work platform of this known system is hinged on the trolleythrough the first and second pairs of connection members, and at theopposite end the work platform is hinged to another trolley on anotheradjacent mast through further pairs of connection members similar tosaid first and second pairs of connection members. As a result the workplatform is allowed to tilt somewhat as it is hoisted or lowered betweenthe two adjacent masts. A levelling device controls the trolley motorson the respective masts in response to sensors sensing the deviation ofthe work platform from a desired normal horizontal position of the workplatform, so that the work platform substantially maintains itshorizontal position during hoisting and lowering. Thus, the known systemis limited to a two-mast configuration.

The prime object of the present invention is to provide a newconstruction hoist system, which is more versatile than the above knownsystem and which is not limited to a two-mast configuration but caninclude a single-mast configuration as well.

Another object of the invention is to provide a versatile constructionhoist system comprising simple and easy-to-use components to facilitatetailor-made configurations of the system for any buildings.

These objects are obtained by the construction hoist system describedinitially, which is characterised by a transport platform having asubstantially flat load carrier floor, and a third pair of connectionmembers provided on the transport platform, the transport platform beingreleasably connectable to the trolley through interconnection of thefirst and third pairs of connection members with the transport platformin a horizontal position in which the load carrier floor is situated ata second level relative the trolley, said second level being below saidfirst level.

As a result, the advantage is obtained that besides the option ofconnecting the work platform, typically of a conventional type with araised work floor, to the trolley there is also the alternative optionof connecting the transport platform, typically with a low load carrierfloor, to the trolley. Said second level relative the trolley issuitably selected so that the load carrier floor of the transportplatform is close to or rests on the ground when the trolley is in itslowermost position on the mast, in order to facilitate materialhandling, i.e. loading and unloading the transport platform.

The construction hoist system of the invention preferably comprises anadapter having said third pair of connection members and beingreleasably connected to the transport platform. The adapter enables useof conventional types of transport platforms, which is cost beneficial.

In accordance with a simple and inexpensive design of the adapter, theadapter comprises a lateral beam, and two spaced apart posts extendingupwardly from the lateral beam, said third pair of connection membersbeing formed on the posts at their upper free ends.

For a single mast configuration, when the transport platform isrelatively short, typically extending not longer than about 1.5 metersfrom the trolley, the construction hoist system of the inventionsuitably comprises a horizontal support beam, which is releasablyattachable to the lateral beam of the adaptor to form a rigid unitconsisting of the support beam and the adaptor. The support beam isreleasably attachable to the trolley in such a manner that the loadcarrier floor of the transport platform is fixed in a horizontalposition when the transport platform is attached to the trolley throughthe support beam.

In the case when the transport platform is relatively long, typicallyfrom two to about six meters, the construction hoist system of theinvention comprises an additonal mast with an additional trolley, and anadditional adapter, which is releasably connected to the transportplatform at an end therof which is opposite the end of the platformwhich is provided with said first-mentioned adapter.

Suitably, said third pair of connection members of the first-mentionedadapter are hingeable on said first pair of connection members of thetrolley and the pair of connection members on the additional adapter arehingeable on an additional pair of connection members on the additionaltrolley, such that the transport platform is tiltable about a horizontalaxis through said third and first pairs of connection members and abouta horizontal axis through the pairs of connection members on theadditional trolley and the additional adapter.

BRIEF DESCRIPTION OF THE DRAWINGS

The construction hoist system of the present invention is explained inmore detail in the following with reference to the accompanyingdrawings, in which

FIG. 1 is a perspective view of a trolley of the construction hoistsystem of the invention,

FIG. 2 is a perspective view of a work platform section fitting thetrolley in FIG. 1,

FIG. 3 is a perspective view of a trolley of the type shown in FIG. 1runing on a left mast, and FIG. 3A is a perspective view of the left endof the work platform of FIG. 2.

FIG. 4 is a perspective view of a trolley of the type shown in FIG. 1running on a right mast, and FIG. 4A is a perspective view of the rightend of the work platform of FIG. 2.

FIG. 5 is a perspective view of a transport platform of the constructionhoist system of the invention,

FIG. 6 is a perspective view of an adapter fitting the trolley in FIG.3,

FIG. 7 is a perspective view of an adapter of the same type as theadapter of FIG. 6, but provided with a support beam and fitting thetrolley of FIGS. 1 and 4, respectively,

FIG. 8 illustrates a two-mast configuration according to theconstruction hoist system of the invention, comprising a transportplatform of the type of FIG. 5 connected to the trolleys of FIGS. 3 and4 with the aid of two adapters of the type shown in FIG. 6, and

FIGS. 9 and 10 illustrate tailor-made examples of the construction hoistsystem of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a trolley 2 in accordance with the construction hoistsystem of the present invention comprising a generally rectangularvertically extending trolley frame 4, guide wheels 6 journalled on thetrolley frame 4, and a platform connection frame 8 rigidly attached tothe trolley frame 4. The platform connection frame 8 has a horizontaltop beam 10, a horizontal lower beam 12, and two side beams 14 taperingfrom the top beam 10 to the lower beam 12. Two upper connection members16 and 18 are mounted on the top beam 10 at opposite ends thereof, and alower connection member 20 in the shape of a bracket is releasablyattached to the lower beam 12. Each upper connection member 18 comprisesa single bracket 18A with a horizontal hinge hole and an adjacent doublebracket 18B with horizontal hinge holes. A mitre-wheel gearing 22 withan electric motor 24 is mounted on the upper part of the trolley frame 4and a safety device 26 of a well-known type is mounted on the lower partof the trolley frame 4. On the lower part of the trolley frame 4 thereis also mounted a level sensor 28 with a lever arm 30.

FIG. 2 shows a rectangular work platform section 32 of a conventionaldesign comprising a work floor 34 and a strengthening frameworkstructure 36 under the work floor 34. As shown in FIG. 2 there are twoupper right connection members 38 and 40 rigidly attached to twoadjacent corners of the work floor 34, two upper left connection members42 and 44 rigidly attached to the other two corners of the rectangularwork floor 34, and lower right and left connection members 46 and 48,respectively, rigidly attached to the lower part of the frameworkstructure 36. Each upper right connection member 38,40 is designed as adouble bracket with horisontal hinge holes, whereas each upper leftconnection member 42,44 is designed as a single bracket with ahorizontal hinge hole. Likewise, the lower right connection member 46 isdesigned as a double bracket, whereas the lower left connection member48 is designed as a single bracket.

The construction hoist system of the invention further comprises atleast one mast 50 having four vertical corner rails 52 and at least onevertical rack 54, see FIG. 4. The trolley 2 runs by means of its guidewheels 6 on two adjacent corner rails 52. A pinion, not shown, of thegearing 22 is in mesh with the rack 54 to enable the motor 24 to drivethe trolley 2 along the mast 50. However, other types of transmissions,such as cable and pulley transmission, may be substituted for thedescribed rack and pinion transmission.

In a single mast configuration, the work platform section 32 is hingedto the trolley 2 by interconnecting the upper right double brackets38,40 of the work platform section 32 and the upper single brackets16A,18A of the connection frame 8 by means of hinge pins, not shown,extending through the horizontal holes of the brackets. In this case thelower right double bracket 46 of the work platform section 32 is securedto the lower bracket 20 of the connection frame 8, so that the workfloor 34 extends horizontally from the trolley 2. As a result, the workfloor 34 is situated at an upper level 55 relative the trolley 2.

If desired, a number of work platforms sections 32 may be interconnectedby means of the brackets 38-48, to form a longer work platform 32, up toabout 19 meters would be possible. In such a case, the constructionhoist system of the invention provides a double mast configuration aswill be explained with reference to FIGS. 3 and 4. The components shownin FIG. 3 which correspond to the components shown in FIGS. 1, 2 and 4have the same reference numerals with the addition of a “prime”. Anadditional mast 50′ with an additional trolley 2′ is provided to beconnected to the left end of the work platform 32. The additionaltrolley 2′ is equivalent to the trolley 2, except that the upperconnection members 16′,18′ of the trolley 2′ are turned upside down, sothat the double brackets 16B′,18B′ are situated above the singlebrackets 16A′,18A′. As a result the upper left single brackets 42,44 ofthe work platform 32 fit the double brackets 16B′,18B′ of the trolley2′.

In the same manner as described above in connection with the single mastconfiguration, the right end of the work platform 32 is hinged to thetrolley 2 by means of the brackets 16A,18A,38,40. The lower bracket 46of the work platform 32 is connected to the lever arm 30. Likewise, theleft end of the work platform 32 is hinged to the trolley 2′. As aresult, the work platform 32 is tiltable about a horizontal axis 56through the brackets 16A,18A,38,40 and about a horizontal axis 58through the brackets 16B′,18B′,42,44. A levelling device, known per se,controls the trolley motors 24,24′ in response to the level sensors28,28′ sensing the deviation of the work platform 32 from a desiredhorizontal position of the work platform, so that the work platform 32substantially maintains its horizontal position during hoisting andlowering.

FIG. 5 shows a rectangular transport platform 60 in accordance with theconstruction hoist system of the invention, comprising a load carrierfloor 62 mounted on a rectangular frame 64. An adapter 66 for thetransport platform 60 comprises two parallel fork elements 68, which areattachable to the frame 64 at each short end of the transport platform60, a lateral beam 70 extending between the fork elements 68, and twospaced apart posts 72 extending vertically upwardly from the lateralbeam 70. Two double brackets 74 and 76 of the same type as the brackets38, 40 on the work platform 32 are attached to the posts 72 at theirupper free ends. A connection element 78 projects from the lateral beam70.

With the transport platform 60 provided with two adapters 66, of whichone has single brackets attached to the posts 72, the transport platform60 is connectable to the trolleys 2 and 2′ in substantially the samemanner as described above for the connection of the work platforms tothe trolleys 2,2′ see FIG. 8. The lever arms 30 and 30′ are attached tothe respective connection elements 78. As a result, the transportplatform is tiltable about the horizontal axes 56 and 58. When thetransport platform 60 is in a horizontal position the carrier load floor62 is situated at a level 80 relative the trolley 2 well below saidlevel 55 of the work floor of the work platform 32.

In the case of a single mast configuration, a support beam 82 isreleasably attached to the adapter 66 as illustrated in FIG. 7. When thetransport platform 60 provided with one adapter 66 is connected to thetrolley 2, the support beam 82 is releasably attached to the lower beam12 of the connection frame 8 on the trolley 2.

Accordingly, the components of the construction hoist system of thepresent invention including masts 50, trolleys 2, work platforms 32,transport platforms 60 and adapters 66 with or without support beams 82enable tailor-made configurations for any buildings, as by way ofexample are schematically illustrated in FIGS. 9 and 10.

What is claimed is:
 1. A construction hoist system, comprising: a singlemast having two adjacent parallel corner rails, a trolley mounted onsaid corner rails to roll up and down on said corner rails, a motor onsaid trolley for driving said trolley along said corner rails, a firstpair of connection members on said trolley, a work platform constructedseparately from said trolley, said work platform including asubstantially flat work floor and a second pair of connection members,said work platform being releasably connected to and fully supported bysaid trolley alone through interconnection of said first and secondpairs of connection members with said work platform in a horizontalposition in which said work floor is situated at a first level relativeto said trolley, a transport platform constructed separately from saidtrolley, said transport platform including a substantially flat loadcarder floor and an adaptor releaseably connected to the transportplatform, said adaptor having a third pair of connection members, saidtransport platform being releasably connected to and fully supported bysaid trolley alone alternatively to said work platform throughinterconnection of said first and third pairs of connection members,said adaptor having a vertical length which allows attachment of saidtransport platform to the trolley in a horizontal position in which saidload carrier floor is situated at a second level relative to saidtrolley, said second level being below said first level.
 2. Aconstruction hoist system comprising: a single mast having two adjacentparallel corner rails, a trolley mounted on said corner rails to roll upand down on said corner rails, a motor on said trolley for driving saidtrolley along said corner rails, a first pair of connection members onsaid trolley, a separate work platform including a substantially flatwork floor and a second pair of connection members, said work platformbeing releasably connectable to and fully supported by said trolleyalone through interconnection of said first and second pairs ofconnection members with said work platform in a horizontal position inwhich said work floor is situated at a first level relative to saidtrolley, a separate transport platform including a substantially flatload carrier floor and a third pair of connection members, saidtransport platform being releasably connectable to and fully supportedby said trolley alone alternatively to said work platform throughinterconnection of said first and third pairs of connection members withsaid transport platform in a horizontal position in which said loadcarrier floor is situated at a second level relative to said trolley,said second level being below said first level, and an adapter havingsaid third pair fo connection members, said adapter being releasablyconnected to said transport platform, wherein said adapter comprises alateral beam, and two spaced apart posts extending upwardly from saidlateral beam, said third pair of connection members being formed on saidposts at their upper free ends.
 3. A construction hoist system accordingto claim 2, further comprising a horizontal support beam, which isreleasably attachable to said lateral beam of said adapter to form arigid unit consisting of said support beam and said adapter, saidsupport beam being releasably attachable to said trolley, such that saidload carrier floor of said transport platform is fixed in a horizontalposition when said transport platform is attached to said trolleythrough said support beam.
 4. A construction hoist system comprising: afirst mast and a second mast, each mast having two adjacent parallelcorner rails, a first trolley and a second trolley mounted,respectively, on said corner rails of said first and second masts toroll upwardly and downwardly on said corner rails of said first mast andsecond mast, respectively, a first motor and a second motor on saidfirst trolley and second trolley, respectively, for driving saidtrolleys along said corner rails, a first pair of connection members onsaid first trolley, a second pair of connection members on said secondtrolley, a work platform including a substantially flat work floor, afirst end and a second end, and a third pair of connection members onsaid work platform at said first end, said work platform beingreleasably connectable to and fully supported by either: said firsttrolley alone through interconnection of said first and third pairs ofconnection members, said second trolley alone through interconnection ofsaid second and third pairs of connection members, or said first andsecond trolleys through interconnection of said first and third pairs ofconnection members and interconnection of said second pair of connectionmembers and a fourth pair of connection members on said work platform atsaid second end, whereby said work floor of said work platform issituated at a first level relative to said first and/or second trolleys,when said work floor extends horizontally, a transport platformincluding a substantially flat load carrier floor, a first end and asecond end, and a fifth pair of connection members provided on saidtransport platform at said first end thereof, said transport platformbeing releasably connectable to and fully supportable either by: saidfirst trolley alone through interconnection of said first and fifthpairs of connection members, said second trolley alone throughinterconnection of said second and fifth pairs of connection members, orsaid first and second trolleys through interconnection of said first andfifth pairs of connection members and interconnection of said secondpair of connection members and a sixth pair of connection membersprovided on said transport platform at said second end thereof, wherebysaid load carrier floor of said transport platform situated at a secondlevel relative to said trolleys below said first level, when said loadcarrier floor extends horizontally, and a first adapter having saidfifth pair of connection members and a second adapter having said sixthpair of connection members, said adapters being releasably connected tosaid transport platform at said first and second ends thereof, whereinsaid first adapter and said second adapter, respectively, comprises alateral beam, and two spaced apart posts extending upwardly from saidlateral beam, said fifth pair of connection members being formed on saidposts of said first adapter at their upper free ends and said sixth pairof connection members being formed on said posts of said second adapterat their upper free ends.
 5. A construction hoist system according toclaim 4, wherein said fifth pair of connection members of said transportplatform are hingeable on said first pair of connection members of saidfirst trolley and said sixth pair of connection members of saidtransport platform are hingeable on said second pair of connectionmembers of said second trolley, such that said transport platform istiltable about a horizontal axis through said fifth and first pairs ofconnection members and about a horizontal axis through said sixth andsecond pairs of connection members.
 6. A construction hoist systemcomprising: a first mast and a second mast, each mast having twoadjacent parallel corner rails, a first trolley and a second trolleymounted, respectively, on said corner rails of said first and secondmasts to roll upwardly and downwardly on said corner rails of said firstmast and second mast, respectively, a first motor and a second motor onsaid first trolley and second trolley, respectively, for driving saidtrolleys along said corner rails, a first pair of connection members onsaid first trolley, a second pair of connection members on said secondtrolley, a work platform constructed separately from said first andsecond trolleys, said work platform including a substantially flat workfloor, a first end and a second end, and a third pair of connectionmembers on said work platform at said first end, said work platformbeing releasably connected to and fully supported by either: said firsttrolley alone through interconnection of said first and third pairs ofconnection members, said second trolley alone through Interconnection ofsaid second and third pairs of connection members, or said first andsecond trolleys through interconnection of said first and third pairs ofconnection members and interconnection of said second pair of connectionmembers and a fourth pair of connection members on said work platform atsaid second end, whereby said work floor of said work platform issituated at a first level relative to said first and/or second trolleys,when said work floor extends horizontally, a transport platformconstructed separately from said first and second trolleys, saidtransport platform including a substantially flat load carrier floor, afirst end and a second end, a first adaptor releaseably connected to thefirst end of the transport platform, and a fifth pair of connectionmembers provided on the first adaptor of said transport platform at saidfirst end thereof, said transport platform being releasably connected toand fully supportable either by: said first trolley alone throughinterconnection of said first and fifth pairs of connection members,said second trolley alone through interconnection of said second andfifth pairs of connection members, or said first and second trolleysthrough interconnection of said first and fifth pairs of connectionmembers and interconnection of said second pair of connection membersand a sixth pair of connection members provided on a second adaptorreleaseably connected to said transport platform at said second endthereof, the adaptors each having a vertical length which allowsattachment of the transport platform to the trolleys, whereby said loadcarrier floor of said transport platform is situated at a second levelrelative to said trolleys below said first level, when said load carrierfloor extends horizontally.
 7. A construction hoist system comprising: afirst mast and a second mast, each of said masts having two rails, afirst trolley and a second trolley running on said rails of said firstmast and second mast, respectively, a first motor and a second motor onsaid first trolley and said second trolley, respectively, for drivingsaid trolleys along said corner rails, a first pair of left and rightconnection members on said first trolley, each of said left and rightconnection members including a first single bracket and a first doublebracket, and being positioned such that said first single bracket isabove said double bracket, a second pair of left and right connectionmembers on said second trolley, each of said second pair of left andright connection members including a second single bracket and a seconddouble bracket, and being positioned such that said double bracket isabove said second single bracket, first and second platforms constructedseparately from said first and second trolleys, each of said platformsincluding a first end and a second end, said first platform including athird pair of double brackets provided at said first and thereof, saidthird pair of double brackets being releasably connected to said firstsingle brackets of said first trolley such that said first platform ispivotable about a first horizontal axis through said first singlebrackets for leveling by a first leveling device mounted on said firsttrolley, and a third pair of single brackets provided on said firstplatform at said second end thereof and releasably connectable to saidsecond double brackets of said second trolley such that said firstplatform is pivotable about a second horizontal axis through said seconddouble brackets for leveling by a second leveling device mounted on saidsecond trolley, the first platform including a first floor situated at afirst level relative to the trolleys, said second platform including afirst adaptor releaseably connected to the first end of the secondplatform and including a fourth pair of double brackets alternativelyreleasably connected to said first single brackets of said first trolleysuch that said second platform is pivotable about the first horizontalaxis through said first single brackets for leveling by the firstleveling device mounted on said first trolley, and a second adaptorreleaseably connected to the second end of the second platform andincluding a fourth pair of single brackets alternatively releasablyconnected to said second double brackets of said second trolley suchthat said second platform is pivotable about the second horizontal axisthrough said second double brackets for leveling by the second levelingdevice mounted on said second trolley, the first and second adaptorseach having a vertical length, whereby the second platform includes asecond floor situated at a second level relative to the trolleys belowthe first level.
 8. A construction hoist system comprising: a first mastand a second mast, each of said masts having two rails, a first trolleyand a second trolley running on said rails of said first mast and secondmast, respectively, a first motor and a second motor on said firsttrolley and said second trolley, respectively, for driving said trolleysalong said corner rails, a first pair of left and right connectionmembers on said first trolley, each of said left and right connectionmembers including a single bracket and a double bracket, and beingpositioned such that said single bracket is above said double bracket, asecond pair of left and right connection members on said second trolley,each of said second pair of left and right connection members includinga single bracket and a double bracket, and being positioned such thatsaid double bracket is above said single bracket, first and secondplatforms, each of said platforms being constructed separately from saidfirst and second trolleys and including: a first end and a second end, apair of double brackets provided at said first end thereof, said pair ofdouble brackets being releasably connected to said single brackets ofsaid first trolley such that said platform is pivotable about a firsthorizontal axis through said single brackets for leveling by a firstleveling device mounted on said first trolley, and a pair of singlebrackets provided at said second end thereof, said pair of singlebrackets being releasably connected to said double brackets of saidsecond trolley such that said platform is pivotable about a secondhorizontal axis through said double brackets for leveling by a secondleveling device mounted on said second trolley, the first platformincluding a first floor situated at a first level relative to thetrolleys, the second platform further including first and secondadaptors releaseably connected, respectively, to the first and secondends thereof, the first and second adaptors including, respectively, thesecond platform's pair of double brackets and pair of single brackets,each of said adaptors having a vertical length which allows anattachment of the second platform to the trolleys in which a secondfloor of the second platform is situated at a second level relative tothe trolleys below the first level.
 9. A construction hoist systemaccording to claim 8, wherein one of said platforms comprises a workplatform having a substantially flat work floor that is situated at afirst level when said work platform is in a horizontal position andconnected to said first and second trolleys, and the other of saidplatforms comprises a transport platform having a substantially flatload carrier floor that is situated at a second level below the firstlevel when said transport platform is in a horizontal position andconnected to said first and second trolleys.
 10. A construction hoistsystem comprising: a first mast and a second mast, each of said mastshaving two rails, a first trolley and a second trolley running on saidrails of said first mast and second mast, respectively, a first motorand a second motor on said first trolley and said second trolley,respectively, for driving said trolleys along said corner rails, a firstpair of left and right connection members on said first trolley, each ofsaid left and right connection members including a single bracket and adouble bracket, and being positioned such that said single bracket isabove said double bracket, a second pair of left and right connectionmembers on said second trolley, each of said second pair of left andright connection members including a single bracket and a doublebracket, and being positioned such that said double bracket is abovesaid single bracket, two different platforms, each of said platformsbeing separate from said first and second trolleys and including, afirst end and a second end, a pair of double brackets provided at saidfirst end thereof, said pair of double brackets being releasablyconnectable to said single brackets of said first trolley such that saidplatform is pivotable about a first horizontal axis therethrough forleveling by a first leveling device mounted on said first trolley, and apair of single brackets provided at said second end thereof, said pairof single brackets being releasably connectable to said double bracketsof said second trolley such that said platform is pivotable about asecond horizontal axis therethrough for leveling by a second levelingdevice mounted on said second trolley, one of said platforms comprisinga work platform having a substantially flat work floor that is situatedat a first level when said work platform is in a horizontal position andconnected to said first and second trolleys, and the other of saidplatforms comprising a transport platform having a substantially flatload carrier floor that is situated at a second level below the firstlevel when said transport platform is in a horizontal position andconnected to said first and second trolleys, and a first adapterreleasably connectable to said transport platform and having said pairof double brackets thereof, and a second adapter releasably connectableto said transport platform and having said pair of single bracketsthereof, wherein said first adapter and said second adapter,respectively, comprises a lateral beam, and two spaced apart postsextending upwardly from said lateral beam and having upper free ends,said pair of double brackets of said first adapter being formed on saidposts at said upper free ends and said pair of single brackets of saidsecond adapter being formed on said posts at said upper free ends.
 11. Aconstruction hoist system comprising: a single mast having two adjacentparallel corner rails, a trolley mounted on said corner rails to roll upand down on said corner rails, a motor on said trolley for driving saidtrolley along said corner rails, a first pair of connection members onsaid trolley, a separate work platform including a substantially flatwork floor and a second pair of connection members, said work platformbeing releasably connectable to and fully supported by said trolleyalone through interconnection of said first and second pairs ofconnection members with said work platform in a horizontal position inwhich said work floor is situated at a first level relative to saidtrolley, a separate transport platform including a substantially flatload carrier floor and a third pair of connection members, saidtransport platform being releasably connectable to and fully supportedby said trolley alone alternatively to said work platform throughinterconnection of said first and third pairs of connection members withsaid transport platform in a horizontal position in which said loadcarrier floor is situated at a second level relative to said trolley,said second level being below said first level, said mast having twoadditional adjacent parallel corner rails, a second trolley rotatablymounted on said additional corner rails whereby the second trolley isfree to run up and down on said additional corner rails, a second motoron said second trolley for driving said second trolley along saidadditional corner rails, and a fourth pair of connection members on saidsecond trolley, said work platform being releasably connectable to saidsecond trolley through interconnection of said second and fourth pairsof connection members with said work platform in a horizontal positionin which said work floor is situated at a first level relative to saidsecond trolley, said work platform being fully supported by said secondtrolley when connected to said second trolley, said transport platformbeing releasably connectable to said second trolley throughinterconnection of said third and fourth pairs of connection memberswith said transport platform in a horizontal position in which said loadcarrier floor is situated at a second level relative to said secondtrolley, said second level relative to said second trolley being belowsaid first level relative to said second trolley, said transportplatform being fully supported by said second trolley when connected tosaid second trolley.